Chapter 14 Water.

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2 Core Case Study: Water Conflicts in the Middle East - A Preview of the FutureMany countries in the Middle East, which has one of the world’s highest population growth rates, face water shortages.Figure 14-1

3 Water Conflicts in the Middle East: A Preview of the FutureMost water in this dry region comes from the Nile, Jordan or Tigris rivers.Countries upstream are building dams and drawing more water…leaving little for downstream countriesCountries are in disagreement as to who has water rights.War could easily erupt in this volatile part of the world

4 Water Conflicts in the Middle East: A Preview of the FutureCurrently, there are no cooperative agreements for use of 158 of the world’s 263 water basins that are shared by two or more countries.Emerging water shortages in many parts of the world – one of the most serious environmental problems

5 WATER’S IMPORTANCE, AVAILABILITY, AND RENEWALNecessary for lifeModerates climate,Sculpts the land,Removes and dilutes wastes and pollutants,Moves continually through the hydrologic cycle.Only about 0.02% of the earth’s water supply is available to us as liquid freshwater.

6 Water One of our most poorly managed resource We waste & pollute itNo substituteLack of safe water & sanitation is leading cause of illness in worldWater quality is worsening

7 Water By The Numbers Oceans: 97% Glaciers / polar ices caps: 1.8%Groundwater: 0.9%Other land surface water (rivers, lakes): 0.017%20% of all surface freshwater is in Lake Baikal, Russia.The Ogallala Aquifer is the largest groundwater reserve.The Middle East has the lowest amount of naturally available freshwater and uses desalination for their water supply.Lake Bikal is the most voluminous freshwater lake in the world.Unbalanced in its distribution. Some areas of land are continually wet, others have not seen permanent water in centuries.The Ogallala Aquifer is located in the central plains of the US because of watershed properties

8 Fresh Water ResourcesFresh waterSurface water 0.3%Ice caps and glaciers77.2%Ground water22.46%Atmospheric water 0.04%Lakes87%Swamps11%Rivers2%Surface waterEarth’s total waterSeawater97 %Fresh water3%Most of the 71% of Earth’s water, more than 1.3 billion cubic kilometers, is contained in the oceans. Only 35 million cubic kilometers is fresh water.Only a tiny amount of the water on Earth is accessible and usable to humans because the ice caps/sheets/ glaciers are the majority of freshwater and are not readily available for use.

10 Groundwater Aquifers–porous rock w/ water flowing throughWater Table – the level of earth’s land crust to which the aquifer is filledRenewability – the circulation rate of groundwater is slow (300 to 4,600 years).

12 The Demand for WaterHumans intervene in the water cycle by utilizing the resource for their own needs.Water is used for consumption, municipal use, in agriculture, in power generation, and for industrial manufacturing.Industry is the greatest withdrawer of water but some of this is returned. Agriculture is the greatest water consumer.Using water often results in its contamination. The supply of potable (drinkable) water is one of the most pressing of the world’s problems.Hydroelectric power generation…Irrigation…Washing, drinking, bathing…

13 Potable WaterPotable water (water suitable to drink) is a rare commodity in large parts of the world.Access to potable water is limited by:ease of distribution, level of water treatment (e.g. sanitation), & amount of available water resources (eg rivers)Countries must deal with problems of removing water borne diseases and dissolved toxins.Once treated, distribution and storage of water becomes important.In many countries, distribution of water is difficult and storage of large amounts almost impossible.Photo: Bob MetcalfWater in many developing nations is difficult to come by, and treatment may be nonexistent.In developed nations, potable water is abundant and treatment is regulated.

14 Comparison of population sizes and shares of the world’s freshwater among the continents.Figure 14-2

15 Global Water Reserves Ogallala AquiferA vast water-table aquifer located beneath the Great Plains in the US. It is extensively used for irrigation. At current usage rates it may be depleted by 2020.North American Great LakesThe largest group of freshwater lakes on Earth, containing 22% of the world's fresh surface water.Mississippi RiverDrains most of the area between the Rocky Mountains and the Appalachians. A series of locks and dams provide for barge traffic.Amazon RiverAccounts for 20% of the world's total river flow and drains 40% of South America. Brazil has the largest supply of freshwater in the world.

16 Global Water Reserves Lake BaikalIs the second most voluminous lake in the world. Contains 20% of the world’s freshwaterVolga RiverWith its many tributaries, drains an area of about million km2 in the most heavily populated part of Russia. High levels of chemical pollution currently give cause for environmental concern.Yangtze RiverFlows 6300 km East China Sea. The Yangtze is subject to extensive flooding, which is only partly controlled by the Three Gorges Dam. It is also heavily polluted.Ganges BasinCentral to the agricultural economy of India. A recent UN report indicates the glaciers feeding the Ganges may disappear by 2030, leaving it as a seasonal system fed by the monsoon rains.Murray-Darling BasinDrains one-seventh of the Australian land mass. Over 70% of Australia's irrigation resources are concentrated there.Congo RiverIs the largest river in Western Central Africa with the second- largest flow in the world. It drains an extensive area of rainforest.

17 Fresh Water UseIntensive agriculture uses large amounts of water, 69% of the freshwater.Improved irrigation techniques can reduce the amount required.Every year huge quantities of water as transported to irrigate crops.Industrial water use increases along with the human population, using about 22% of freshwater.The cooling of power plants and the processing of almost all commercial goods requires the use the water.Manufacturing and production processes are usually water intensive. Some everyday items use surprisingly large amounts of water in their production.Irrigation accounts for 69%We currently use more than 50% of the world’s reliable runoff of surface water and could be using 70-90% by 2025.About 70% of the water we withdraw from rivers, lakes, and aquifers is not returned to these sources.Global rates of water withdrawal from surface and groundwater sources are projected to more than double in the next two decades as a result of increased population growth and economic development.Industrial treatment uses 22%An automobile:380,000 litersof water

18 Municipal supply is about 8%Municipal Water Use454 g of grain-fedbeef: 3,000 litersof waterCities and residences use only 8% of the freshwater. Nearly half of the municipal water in the US is used to flush toilets or water lawns.Another 20-35% is lost in water leaks.Large savings can be made by improving the efficiency of water use.Treatment of waste water is a major issue.The cotton in a pair of jeans: 6,800 liters of waterSTOPDescribe TWO practical measures that a family could take that would reduce their overall water use at home.Municipal supply is about 8%

19 Agricultural Water UseWater Use: AmericaIndustrial Water UseCubic meters per person per yearAgricultural Water UseCubic meters per person per yearPer capita = per personDomestic Water UseCubic meters per person per yearSource: Worldwater.org

20 Agricultural Water UseWater Use: AfricaDomestic Water UseAgricultural Water UseIndustrial Water UseCubic meters per person per yearCubic meters per person per yearCubic meters per person per yearSource: Worldwater.org

21 Agricultural Water UseIndustrial Water UseCubic meters per person per yearWater Use: AsiaAgricultural Water UseCubic meters per person per yearDomestic Water UseCubic meters per person per yearSource: Worldwater.org

22 Agricultural Water UseWater Use: EuropeDomestic Water UseAgricultural Water UseIndustrial Water UseCubic meters per person per yearCubic meters per person per yearCubic meters per person per yearSource: Worldwater.org

23 Agricultural Water UseWater Use: OceaniaAgricultural Water UseIndustrial Water UseCubic meters per person per yearDomestic Water UseCubic meters per person per yearCubic meters per person per yearSource: Worldwater.org

24 WATER’S IMPORTANCE, AVAILABILITY, AND RENEWALSome precipitation infiltrates the ground and is stored in soil and rock (groundwater).Water that does not sink into the ground or evaporate into the air runs off (surface runoff) into bodies of water.The land from which the surface water drains into a body of water is called its watershed or drainage basin.

25 Unconfined Aquifer Recharge Area Evaporation and transpirationPrecipitationEvaporation and transpirationEvaporationConfined Recharge AreaRunoffFlowing artesian wellRecharge Unconfined AquiferStream Well requiring a pumpFigure 14.3Natural capital: groundwater system. An unconfined aquifer is an aquifer with a permeable water table. A confined aquifer is bounded above and below by less permeable beds of rock where the water is confined under pressure. Some aquifers are replenished by precipitation; others are not.InfiltrationWater tableLakeInfiltrationUnconfined aquiferLess permeable material such as clayConfined aquiferConfining impermeable rock layerFig. 14-3, p. 308

26 WATER’S IMPORTANCE, AVAILABILITY, AND RENEWALWe currently use more than half of the world’s reliable runoff of surface water and could be using 70-90% by 2025.About 70% of the water we withdraw from rivers, lakes, and aquifers is not returned to these sources.Irrigation is the biggest user of water (70%), followed by industries (20%) and cities and residences (10%).

27 Water in the United StatesAverage precipitation (top) in relation to water-deficit regions and their proximity to metropolitan areas (bottom).Figure 14-4

28 Average annual precipitation (centimeters)Less than 4181–12241–81More than 122Figure 14.4Natural capital: average annual precipitation and major rivers (top) and water-deficit regions in the continental United States and their proximity to metropolitan areas having populations greater than 1 million (bottom). QUESTION: What is the water supply situation where you live or go to school? (Data from U.S. Water Resources Council and U.S. Geological Survey)Fig. 14-4a, p. 309

29 Metropolitan regions with population greater than 1 millionFigure 14.4Natural capital: average annual precipitation and major rivers (top) and water-deficit regions in the continental United States and their proximity to metropolitan areas having populations greater than 1 million (bottom). QUESTION: What is the water supply situation where you live or go to school? (Data from U.S. Water Resources Council and U.S. Geological Survey)Acute shortageShortageAdequate supplyMetropolitan regions with population greater than 1 millionFig. 14-4b, p. 309

30 Case Study: Freshwater Resources in the United States17 western states by 2025 could face intense conflict over scarce water needed for urban growth, irrigation, recreation and wildlife.Figure 14-5

31 Highly likely conflict potential Substantial conflict potential Wash.MontanaN.D.OregonIdahoWyomingS.D.NevadaNeb.UtahKansasColo.CaliforniaOak.Figure 14.5Natural capital degradation: water hot spot areas in 17 western states that by 2025 could face intense conflicts over scarce water needed for urban growth, irrigation, recreation, and wildlife. Some analysts suggest that this is a map of places not to live over the next 25 years. QUESTION: Do you live or would you live in one of these hotspot areas? (Data from U.S. Department of the Interior)N.M.TexasHighly likely conflict potentialSubstantial conflict potentialModerate conflict potentialUnmet rural water needsFig. 14-5, p. 310

32 TOO LITTLE FRESHWATERAbout 41% of the world’s population lives in river basins that do not have enough freshwater.Many parts of the world are experiencing:Rivers running dry.Lakes and seas shrinking.Falling water tables from overpumped aquifers.

33 Stress on the World’s River BasinsComparison of the amount of water available with the amount used by humans.Figure 14-6

34 Case Study: Who Should Own and Manage Freshwater ResourcesThere is controversy over whether water supplies should be owned and managed by governments or by private corporations.European-based water companies aim to control 70% of the U.S. water supply by buying up water companies and entering into agreements with cities to manage water supplies.

35 TOO LITTLE FRESHWATERCities are outbidding farmers for water supplies from rivers and aquifers.Countries are importing grain as a way to reduce their water use.More crops are being used to produce biofuels.Our water options are:Get more water from aquifers and rivers, desalinate ocean water, waste less water.

36 WITHDRAWING GROUNDWATER TO INCREASE SUPPLIESMost aquifers are renewable resources unless water is removed faster than it is replenished or if they are contaminated.Groundwater depletion is a growing problem mostly from irrigation.At least one-fourth of the farms in India are being irrigated from overpumped aquifers.

37 Withdrawing GroundwaterTrade-OffsWithdrawing GroundwaterAdvantagesDisadvantagesUseful for drinking and irrigationAquifer depletion from overpumpingSinking of land (subsidence) from overpumpingAvailable year-roundExists almost everywherePolluted aquifers for decades or centuriesRenewable if not overpumped or contaminatedSaltwater intrusion into drinking water supplies near coastal areasFigure 14.7Trade-offs: advantages and disadvantages of withdrawing groundwater. QUESTION: Which two advantages and which two disadvantages do you think are the most important?No evaporation lossesReduced water flows into surface watersIncreased cost and contamination from deeper wellsCheaper to extract than most surface watersFig. 14-7, p. 313

38 Human EffectsMost water used by humans comes from rivers, lakes, & aquifers.Damming rivers for electricity affects water flow downstream as seen in the James Bay project in Quebec with over 600 dams blocking 19 rivers.Irrigation and diversions for drinking water displace vast amounts of the water for these resource stores.Pollution from fertilizers, waste, an sewage can have paralyzing effects on rivers, lakes, and oceans.These actions can have dramatic effects on the habitats and can cause loss of biodiversity.Irrigation can move move millions of liters of water from rivers and aquifers, affecting land down stream.Damming and diverting rivers lowers the availability of water downstream and stops annual floods that replace soil nutrients.Dams, locks and other obstacles make it very difficult for migratory fish to find their way to breeding grounds.

39 Rivers as HighwaysThe major rivers of the worlds provide water for irrigation and drinking and enable the transport of large amounts of freight especially when dammed.Huge barges moved by tugboats are used on many rivers and lakes of developed countries.However there are many negative environmental effects.Some rivers such as the Yangtze are so polluted and congested with ships that little can live in them.The Yangtze River Dolphin was last seen in 2002 and has since been declared functionally extinct. It is the first cetacean extinction directly attributable to human interference.Mississippi River, USAPhoto: Ryu Cheoi Creative Commons Attribution ShareAlike 3.0Yangtze River, China

40 Groundwater Depletion: A Growing ProblemAreas of greatest aquifer depletion from groundwater overdraft in the continental U.S.The Ogallala, the world’s largest aquifer, is most of the red area in the center (Midwest).Figure 14-8

41 Other Effects of Groundwater OverpumpingGroundwater overpumping can cause land to sink, and contaminate freshwater aquifers near coastal areas with saltwater.Figure 14-11

45 Groundwater DepletionSolutionsGroundwater DepletionPreventionControlWaste less waterRaise price of water to discourage wasteSubsidize water conservationBan new wells in aquifers near surface watersTax water pumped from wells near surface watersBuy and retire groundwater withdrawal rights in critical areasFigure 14.12Solutions: ways to prevent or slow groundwater depletion by using water more sustainably. QUESTION: Which two of these solutions do you think are the most important?Set and enforce minimum stream flow levelsDo not grow water-intensive crops in dry areasFig , p. 316

46 USING DAMS AND RESERVOIRS TO SUPPLY MORE WATERLarge dams and reservoirs can produce cheap electricity, reduce downstream flooding, and provide year-round water for irrigating cropland, but they also displace people and disrupt aquatic systems.

49 Provides water for year-round irrigation of cropland Flooded land destroys forests or cropland and displaces peopleLarge losses of water through evaporationProvides water for drinkingDownstream cropland and estuaries are deprived of nutrient-rich siltReservoir is useful for recreation and fishingRisk of failure and devastating downstream floodingCan produce cheap electricity (hydropower)Figure 14.13Trade-offs: advantages (green) and disadvantages (orange) of large dams and reservoirs. The world’s 45,000 large dams (higher than 15 meters or 50 feet) capture and store 14% of the world’s runoff, provide water for almost half of all irrigated cropland, and supply more than half the electricity used by 65 countries. The United States has more than 70,000 large and small dams, capable of capturing and storing half of the country’s entire river flow. QUESTION: Which single advantage and which single disadvantage do you think are the most important?Downstream flooding is reducedMigration and spawning of some fish are disruptedFig a, p. 317

50 Powerlines Reservoir Dam Powerhouse Intake Turbine Fig. 14-13b, p. 317Figure 14.13Trade-offs: advantages (green) and disadvantages (orange) of large dams and reservoirs. The world’s 45,000 large dams (higher than 15 meters or 50 feet) capture and store 14% of the world’s runoff, provide water for almost half of all irrigated cropland, and supply more than half the electricity used by 65 countries. The United States has more than 70,000 large and small dams, capable of capturing and storing half of the country’s entire river flow. QUESTION: Which single advantage and which single disadvantage do you think are the most important?Fig b, p. 317

51 Case Study: The Colorado Basin – an Overtapped ResourceThe Colorado River has so many dams and withdrawals that it often does not reach the ocean.14 major dams and reservoirs, and canals.Water is mostly used in desert area of the U.S.Provides electricity from hydroelectric plants for 30 million people (1/10th of the U.S. population).

52 Case Study: The Colorado Basin – an Overtapped ResourceLake Powell, is the second largest reservoir in the U.S.It hosts one of the hydroelectric plants located on the Colorado River.Figure 14-15

53 The Colorado River BasinThe area drained by this basin is equal to more than one-twelfth of the land area of the lower 48 states.Figure 14-14

54 Case Study: China’s Three Gorges DamThere is a debate over whether the advantages of the world’s largest dam and reservoir will outweigh its disadvantages.The dam will be 2 kilometers long.The electric output will be that of 18 large coal-burning or nuclear power plants.It will facilitate ship travel reducing transportation costs.Dam will displace 1.2 million people.Dam is built over seismatic fault and already has small cracks.

55 Three Gorges DamPhoto: Christoph FlinkoBl Creative Commons Attribution ShareAlike 3.0The Three Gorges Dam spans the Yangtze River at Sandouping, China, and is the largest hydroelectric dam in the world, capable of producing 22,500MW of electricity.Major construction began in 1994 and is expected to be fully completed by 2011.Photo: Guuganji Creative Commons Attribution ShareAlike 3.0

56 Satellite image of Three Gorges Dam 1987, before construction.Filling the DamThe reservoir behind the Three Gorges Dam extends 600km upstream. The dam itself is over 2km wide and 186m high.Satellite image of Three Gorges Dam 1987, before construction.Image: NASA

60 Dam RemovalSome dams are being removed for ecological reasons and because they have outlived their usefulness.In 1998 the U.S. Army Corps of Engineers announced that it would no longer build large dams and diversion projects in the U.S.The Federal Energy Regulatory Commission has approved the removal of nearly 500 dams.Removing dams can reestablish ecosystems, but can also re-release toxicants into the environment.

61 TRANSFERRING WATER FROM ONE PLACE TO ANOTHERTransferring water can make unproductive areas more productive but can cause environmental harm.Promotes investment, jobs and strong economy.It encourages unsustainable use of water in areas water is not naturally supplied.

64 Case Study: The Aral Sea DisasterDiverting water from the Aral Sea and its two feeder rivers mostly for irrigation has created a major ecological, economic, and health disaster.About 85% of the wetlands have been eliminated and roughly 50% of the local bird and mammal species have disappeared.Since 1961, the sea’s salinity has tripled and the water has dropped by 22 meters most likely causing 20 of the 24 native fish species to go extinct.

65 Aswan High DamTwo dams straddle the Nile River at Aswan, Egypt. The Aswan High Dam was completed in 1970 and formed Lake Nasser. which is 550 km long and capable of holding two years of the Nile's annual flow.The main objectives of the project were:energy generation in a renewable form.flood control in downstream locations.provision of water for agriculture and domestic use.A serious detrimental effect is the loss of the annual floods downstream. These used to replenish the nutrients of the flood plain and flush out accumulated salts.Wiki Commons

66 Aswan High DamWithout flooding, fertilizers must be applied to the land and salts build up in the soils, causing crops to fail.Without annual deposition of river sediments because of build- up behind the dam, the land is eroding, allowing the sea to encroach up the river delta.Damming has also caused 64% of commercially fished species in the Nile to disappear.Time will tell if better management will help to reverse the problems currently being experienced in the Nile Delta region.Photo: NASA

67 DESALTING SEAWATER, SEEDING CLOUDS, AND TOWING ICEBERGS AND GIANT BAGGIESRemoving salt from seawater by current methods is expensive and produces large amounts of salty wastewater that must be disposed of safely.Distillation: heating saltwater until it evaporates, leaves behind water in solid form.Reverse osmosis: uses high pressure to force saltwater through a membrane filter.

68 DESALTING SEAWATER, SEEDING CLOUDS, AND TOWING ICEBERGS AND GIANT BAGGIESSeeding clouds with tiny particles of chemicals to increase rainfall towing icebergs or huge bags filled with freshwater to dry coastal areas have all been proposed but are unlikely to provide significant amounts of freshwater.

69 INCREASING WATER SUPPLIES BY WASTING LESS WATERWe waste about two-thirds of the water we use, but we could cut this waste to 15%.65-70% of the water people use throughout the world is lost through evaporation, leaks, and other losses.Water is underpriced through government subsidies.The lack of government subsidies for improving the efficiency of water use contributes to water waste.

70 Water Conservation StrategiesIrrigation techniques:Employ micro/drip irrigationIrrigate at times of less low evaporation (eg. Night)Choose crops that do not require irrigation in certain climatesAgricultural & other methods:Incorporate shelterbelts or windbreaksReduce runoff by contour planting, strip cropping, and terracingCover surface with mulch to prevent evaporationEat less meatMigratory birds will lose their wetland habitats that are critical for their reproduction and survival.Center pivot (above) and gravity flow (below) are not as efficient as drip irrigation that allows water to trickle to the roots.

71 INCREASING WATER SUPPLIES BY WASTING LESS WATERSixty percent of the world’s irrigation water is currently wasted, but improved irrigation techniques could cut this waste to 5-20%.Center-pivot, low pressure sprinklers sprays water directly onto crop.It allows 80% of water to reach crop.Has reduced depletion of Ogallala aquifer in Texas High Plains by 30%.Drip Irrigation is the most efficient method

72 (efficiency 60% and 80% with surge valves)Drip irrigation(efficiency 90–95%)Gravity flow(efficiency 60% and 80% with surge valves)Figure 14.18Major irrigation systems: because of high initial costs, center-pivot irrigation and drip irrigation are not widely used. The development of new low-cost drip-irrigation systems may change this situation.Center pivot(efficiency 80%–95%)Water usually pumped from underground and sprayed from mobile boom with sprinklers.Above- or below-ground pipes or tubes deliver water to individual plant roots.Water usually comes from an aqueduct system or a nearby river.Fig , p. 325

73 Reducing Irrigation Water WasteSolutionsReducing Irrigation Water Waste• Line canals bringing water to irrigation ditches• Level fields with lasers• Irrigate at night to reduce evaporation• Monitor soil moisture to add water only when necessary• Polyculture• Organic farmingFigure 14.19Solutions: methods for reducing water waste in irrigation. QUESTION: Which two of these solutions do you think are the most important?• Don't grow water-thirsty crops in dry areas• Grow water-efficient crops using drought resistant and salt-tolerant crop varieties• Irrigate with treated urban waste water• Import water-intensive crops and meatFig , p. 326

74 Solutions: Getting More Water for Irrigation in Developing Countries – The Low-Tech ApproachMany poor farmers in developing countries use low-tech methods to pump groundwater and make more efficient use of rainfall.Figure 14-20

75 Solutions Reducing Water Waste • Redesign manufacturing processes• Repair leaking underground pipes• Landscape yards with plants that require little water• Use drip irrigation• Fix water leaks• Use water meters• Raise water prices• Use waterless composting toilets• Require water conservation in water-short citiesFigure 14.21Solutions: methods of reducing water waste in industries, homes, and businesses. QUESTION: Which three of these solutions do you think are the most important?• Use water-saving toilets, showerheads, and front loading clothes washers• Collect and reuse household water to irrigate lawns and nonedible plants• Purify and reuse water for houses, apartments, and office buildings• Don't waste energyFig , p. 327

76 Raising the Price of Water: A Key to Water ConservationWe can reduce water use and waste by raising the price of water while providing low lifeline rates for the poor.When Boulder, Colorado introduced water meters, water use per person dropped by 40%.A 10% increase in water prices cuts domestic water use by 3-7%.

77 Solutions: Using Less Water to Remove Industrial and Household WastesWe can mimic the way nature deals with wastes instead of using large amounts of high-quality water to wash away and dilute industrial and animal wastes.Use nutrients in wastewater before treatment as soil fertilizer.Use waterless and odorless composting toilets that convert human fecal matter into a small amount of soil material.

78 TOO MUCH WATERHeavy rainfall, rapid snowmelt, removal of vegetation, and destruction of wetlands cause flooding.Floodplains, which usually include highly productive wetlands, help provide natural flood and erosion control, maintain high water quality, and recharge groundwater.To minimize floods, rivers have been narrowed with levees and walls, and dammed to store water.

79 TOO MUCH WATERComparison of St. Louis, Missouri under normal conditions (1988) and after severe flooding (1993).Figure 14-22

80 TOO MUCH WATERHuman activities have contributed to flood deaths and damages.Figure 14-23

81 Oxygen released by vegetationForested HillsideOxygen released by vegetationDiverse ecological habitatEvapotranspirationTrees reduce soil erosion from heavy rain and windAgricultural landSteady river flowFigure 14.23Natural capital degradation: hillside before and after deforestation. Once a hillside has been deforested for timber and fuelwood, livestock grazing, or unsustainable farming, water from precipitation rushes down the denuded slopes, erodes precious topsoil, and can increase flooding in local streams. Such deforestation can also increase landslides and mudflows. A 3,000-year-old Chinese proverb says, “To protect your rivers, protect your mountains.”Leaf litter improves soil fertilityTree roots stabilize soil and aid water flowVegetation releases water slowly and reduces floodingFig a, p. 330

82 Evapotranspiration decreases Roads destabilize hillsidesAfter DeforestationTree plantationEvapotranspiration decreasesRoads destabilize hillsidesRanching accelerates soil erosion by water and windWinds remove fragile topsoilGullies and landslidesAgricultural land is flooded and silted upFigure 14.23Natural capital degradation: hillside before and after deforestation. Once a hillside has been deforested for timber and fuelwood, livestock grazing, or unsustainable farming, water from precipitation rushes down the denuded slopes, erodes precious topsoil, and can increase flooding in local streams. Such deforestation can also increase landslides and mudflows. A 3,000-year-old Chinese proverb says, “To protect your rivers, protect your mountains.”Heavy rain leaches nutrients from soil and erodes topsoilRapid runoff causes floodingSilt from erosion blocks rivers and reservoirs and causes flooding downstreamFig b, p. 330

83 Preserve forests on watersheds SolutionsReducing Flood DamagePreventionControlPreserve forests on watershedsStrengthen and deepen streams (channelization)Preserve and restore wetlands in floodplainsBuild levees or floodwalls along streamsTax all development on floodplainsFigure 14.24Solutions: methods for reducing the harmful effects of flooding. QUESTION: Which two of these solutions do you think are the most important?Use floodplains primarily for recharging aquifers, sustainable agriculture and forestry, and recreationBuild damsFig , p. 331

84 SOLUTIONS: USING WATER MORE SUSTAINABLYWe can use water more sustainably by cutting waste, raising water prices, preserving forests and wetlands in water basins, and slowing population growth.Figure 14-25

85 What Can You Do? Water Use and Waste• Use water-saving toilets, showerheads, and faucet aerators.• Shower instead of taking baths, and take short showers.• Stop water leaks.• Turn off sink faucets while brushing teeth, shaving, or washing.• Flush toilets only when necessary.• Wash only full loads of clothes or use the lowest water-level for smaller loads.• Use recycled (gray) water for lawn, gardens, house plants, car washing.• Wash a car from a bucket of soapy water, and use the hose for rinsing only.Figure 14.25Individuals matter: ways you can reduce your use and waste of water. Visit for an array of water-saving tips from the EPA and the California Urban Water Conservation Council that can be used anywhere. QUESTION: Which four of these actions do you think are the most important?• If you use a commercial car wash, try to find one that recycles its water.• Replace your lawn with native plants that need little if any watering and decorative gravel or rocks.• Water lawns and gardens in the early morning or evening.• Sweep or blow off driveways instead of hosing off with water.• Use drip irrigation and mulch for gardens and flowerbeds.Fig , p. 333